Page 320 - The Secret War in the Italian front in WWI (1915-1918)

THE SECRET WAR ON THE ITALIAN FRONT IN WWI (1915 – 1918)

The instructions of the T1 show it adopted double transposition methods with a 9-letter key changed
daily according to tables distributed to radiotelegraphic stations every month . The drafter of the
10
instructions, probably Sacco himself, recommended to implement double transposition, because
“the single one would make decoding easier to the enemy and therefore had to be strictly forbidden”
(picture.14.2) .
11
Similar ciphers were already widely used, especially throughout the German army from the first
months of the war. For instance, the French analysts managed to decrypt dispatches coded by
the German ÜBCHI cipher, mainly because their enemies left the keys unchanged for several
days, increasing the probability of detecting telegrams of equal length within a large amount of
cryptographic material: indeed, a prerequisite to apply a decoding process known as ‘multiple
anagrams technique’ which was already known at the end of the 19 century .
th
12
Conversely, a long enough key replaced daily posed serious obstacles to the double transposition
forcing, especially if encoding was producing ‘incomplete rectangles’ and provided, of course,
that the operators avoided carelessness and errors in encoding . Combined with the scarcity
13
of cryptographic material, this explains why the Austrian crypto analysts never mention the T1
chipher.
The ciphering system was sound enough to remain valid after the war, at least through 1919. The
T2 version introduced in April of that year, used keys with variable length between 8 to 10 letters,
instead of exactly 9, replaced any other day .
14

14.2 OTHER RELEVANT PRODUCTS OF THE CRYPTOGRAPHIC UNIT

The InTer-allIed code (I.a.)

By November 1917, six French and five British divisions had arrived in Italy and reached the front
lines by the end of December 1917. In the spring of the following year, part of these troops returned
to the western front while three French and two British divisions remained in Italy to fight.
Their telecommunications systems had to be linked with those of the Italian army to ensure rapid
and effective communication between Staffs and then among the units deployed to adjacent sectors
on the front. As of wireless communications, compatibility of frequencies and a suitable three-
language code, known as I.A. code, had to be arranged.
Section R’s logs of 8 December 1917, reported that, on the previous day, Major Sacco had reached
the Headquarters of the Supreme Command in Padua “to settle the issue of drafting and using
ciphers for correspondence with the French and British allies” . During the four-day mission, the
15
foundations were laid to adopt the inter-allied code and the Italian Cryptographic Unit was tasked

10 Library of the ISCAG, coll. XXXI A, n° 11129. The key was a 9-letter word transformed into a numeric key through the
method explained in the previous chapters.
11 ibidem.
12 F. L. Bauer, op. cit. p.95 - 98; 421 - 423. This method can be applied to all transposition systems. It consists of superimposing
two or more messages of equal length and then putting together pairs of columns with the purpose of finding the one with the
most likely bi-grams in the language of the messages. The chosen columns are then put together with the remaining columns
to find the group with the most likely tri-grams. One should be able to start seeing fragments of the messages in plain text, to
which the remaining columns of the cryptograms are approached one after another to find the messages’ content.
13 The examples in the T1 Instruction Handbook portrayed only incomplete rectangles, that is, the last row had variable length
based on the number of letters contained in the messages, as it happens with a fixed columns number.
14 The double transposition with frequently variable key found large application during the WWII too.
15 Section R logs, 7 December 1917, AUSSME, Series B1, 101S, Vol. 307d.

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